Unocttrium
Unocttrium, Uot, is the temporary name for element 183. NUCLEAR What follows is based on a first-order, liquid-drop assessment of where the outer boundary of the nuclear world is. Assume cautious values for how many neutrons a nucleus with 183 protons can bind (high neutron dripline) and how few it can have before it fissions immediately regardless of how much the structure it can develop stabilizes it (low must-fission curve). Assume, too, that anything that lasts long enough so that protons and neutrons can be treated as particles rather than collections of quarks (is causal) might be a nucleus. Under these conditions, Uot isotopes are theoretically possible between Uot 455 and Uot 800 (see "The Final Element", this wiki). Uot 455 through Uot 640 are expected to decay by beta emission if they don’t fission quickly. Above that value of A, the confident neutron dripline, drops may decay by neutron emission before they can fission. (Structural correction does not affect neutron emission.) Uot 640 itself requires 1.5 MeV of structural correction energy to survive for the 10^-14 sec needed to bind an electron and so qualify as a nucleus. Uot 731 and heavier don’t require any correction. Isotopes lighter than Uot 479 need more than twice the correction energy needed to prevent fission in worst-case nuclei in the A = 480 region(1). In between, it is not usually possible to determine whether structural corrections will stabilize nuclear drops against fission. Neutron shell closures have been predicted at N = 406(2),(3),(4), 370(4), 318(5), and 308(1). The isotope Uot 589 requires 2.5 MeV of structural correction, which means some isotopes in the Uot 579 to Uot 594 band are likely. Uot 553 requires 6 MeV of structural correction, which means some isotopes in the band Uot 543 to Uot 558 are also likely. Long beta-decay half-lives in this band are possible, so decay by alpha emission is likely. Uot 501 requires 18 MeV of correction energy and Uot 491 requires 21.5 MeV, which implies that nuclides in these regions are unlikely. Between Uot 479 and Uot 682 some drops may be nuclei. Outside this band, isotopes of Uot are nearly impossible. ATOMIC Electron structure of Uot has not been studied closely, but it is likely to differ significantly from the conventional orbitals found in lower-Z nuclei. While only the innermost electrons would be qualitatively different, other electrons are likely to be quantitatively different from those in lower-Z atoms. Uot is also large enough that nuclear shape may have an effect on electron structure, which might cause different isotopes of Uot to have different electronic structures. (That means it is no longer an element in the chemical sense.) Predictions of atomic or chemical properties of Uot are risky. FORMATION Ions of this element may form when material from roughly 1 km depth is ejected from a disintegrating neutron star during a merger. It is probably impossible for lighter isotopes to form in this way. Fusion or multinucleon transfer reactions in the polar jets emanating from a neutron star or black hole might produce lighter isotopes, including those in the Uot 579 to Uot 594 and Uot 543 to Uot 558 bands. Quantities amount to a few atoms per star at best. REFERENCES 1. "Decay Modes and a Limit of Existence of Nuclei"; H. Koura; 4th Int. Conf. on the Chemistry and Physics of Transactinide Elements; Sept. 2011. 2. "Magic Numbers of Ultraheavy Nuclei"; V. Yu Denisov; Physics of Atomic Nuclei, v. 68, no. 7, pp 1133-1137; 2005. 3. “Search for Superheavy Elements Among Fossil Fission Tracks in Zircon”; J. Maly & D.R. Walz; Stanford Linear Accelerator Center publication SLAC-PUB-2554; July 1980. 4. “Single Particle Levels of Spherical Nuclei in the Superheavy and Extremely Superheavy Mass Region”; H. Koura and S. Chiba; Journal of the Physical Society of Japan; DOI 10.7566/JPSJ.82.014201; Jan. 2013. 5. “The Highest Limiting Z in the Extended Periodic Table”; Y.K. Gambhir, A. Bhagwat, and M. Gupta; Journal of Physics G: Nuclear and Particle Physics. 42 (12): 125105. DOI:10.1088/0954 3899/42/12/ 125105. (12-08-19)